homeostasis

• negative feedback - increase in body temperature

  1. body temperature increases
  2. increase is detected by the hypothalamus in the brain
  3. increased sweating and vasodilation
  4. body cools
  5. normal body temperature is restored
• negative feedback - decrease in body temperature

  1. body temperature decreases
  2. decrease is detected by hypothalamus in the brain
  3. increased shivering and vasocontriction
  4. body temperature rises
  5. normal body temperature is restored
• homeostasis - is the maintenance of a constant internal environment despite changes in the external environment
• homeostasis is controlled by the nervous system, hormones and the endocrine system
• pancreas - the endocrine (secretes hormones) and exocrine (secretes digestive enzymes) glands
• endocrine function of the pancreas:

  • hormones are secreted from the cells in the Islet of Langerhans
  • alpha cells manufacture and secrete the hormone glucagon
  • beta cells manufacture and secrete the hormone insulin
  • they are released directly into the blood
• exocrine function of the pancreas:

  • pancreatic cells surround small tubules which drain into the pancreatic duct
  • pancreatic cells produce pancreatic juice which is made up of amylase, lipids and trypsinogen which is inactive protease
• state the three sources of glucose

  • directly from the diet - glucose enters blood when carbohydrates are broken down
  • breakdown of glycogen - glycogenolysis
  • gluconeogenesis - production of new glucose from sources other than carbohydrates
• the negative feedback of when there is a rise in blood glucose concentration

  1. pancreas detects the blood glucose concentration is too high
  2. beta cells secrete insulin and alpha cells stop secreting glucagon
  3. so: cells take up more glucose, gluconeogenesis is activated and cells respire more glucose
  4. less glucose in the body
• the negative feedback of when there is a fall in blood glucose concentration

  1. pancreas detects blood glucose concentration is too low
  2. alpha cells secrete glucagon and beta cells stop secreting insulin
  3. glucagon binds to receptors on liver cells
  4. so: glycogenolysis is activated, gluconeogenesis is activated and so cells respire less glucose
  5. cells release glucose into the blood
• beta cells - secrete insulin into the blood
• alpha cells - secrete glucagon into the blood
• the action of insulin - lowers blood glucose concentration when it is too high

  1. insulin binds to specific receptors on the cell membranes of liver cells and muscle cells
  2. it increases the permeability of muscle-cell membranes to glucose so the cells take up more glucose and this involves increasing the number of protein channels in the cell membrane
  3. insulin also activates enzymes in the liver and muscle cells that converts glucose into glycogen which is glycogenesis
  4. increases the rate of respiration of glucose
• the action of glucagon - raises the blood glucose concentration when it is too low

  1. glucagon binds to specific receptors on the cell membranes of liver cells
  2. glucagon activates enzymes in liver cells that break down glycogen into glucose which is known as glycogenolysis
  3. glucagon also activates enzymes that are involved in the formation of glucose from glycerol and amino acids this is known as gluconeogenesis
  4. decreases the rate of respiration of glucose
• glycogenesis - the synthesis of glycogen from glucose
• glycosgenolysis - the breakdown of glycosidic bonds in the formation of glucose
• gluconeogenesis - the process of making glucose from non-carbohydrate sources
• how does insulin increase the permeability of skeletal/cardiac muscle cell membranes?

  1. insulin binds to receptors on cell membranes
  2. stimulates GLUT4 glucose transporters to move and fuse with membrane
  3. glucose transported int cell by facilitated diffusion
• more adrenaline = more glucose = more energy = more muscle contraction
• explain the second messenger model

  1. adrenaline fuses on the cell membrane of liver cells
  2. this activates Adenylate cyclase
  3. this causes the conversion of ATP to Cyclic AMP (the second messenger)
  4. which activates protein kinase
  5. this causes glycogen to be broken down into glucose
• hormones are proteins that are produced by the endocrine system and travel through the bloodstream to the target cells and these are complementary receptors to specific hormones
• what is type 1 diabetes?

  where the immune system attacks Beta cells in the islets of Langerhans so they are unable to produce insulin
• why is there some glucose in the urine of type 1 diabetics?

  the kidneys cant re-absorb all the excess glucose that is in the blood
• what is hyperglycaemia?

  High blood glucose concentration
• what causes hyperglycemia?

  insulin resistance, pancreas not producing enough insulin
• how is type 1 diabetes treated?

  1. insulin injections
  2. insulin therapy
  3. insulin pump
  4. eating regular meals
  5. avoiding too much simple carbohydrates
• why should type 1 diabetics avoid simple carbohydrates?

  simple carbohydrates are more easily broken down so the blood glucose concentration would increase rapidly which would cause hyperglycaemia
• what is type 2 diabetes?

  when beta cells don't produce enough insulin or when the body doesn't respond properly to insulin as the receptors aren't functioning properly so the cells don't take up enough glucose
• what are the risk factors of type 2 diabetes?

  • lack of exercise
  • poor diet
  • age
  • obesity
  • family history
• how can type 2 diabetes be treated?

  • eating a healthy balanced diet
  • loosing weight
  • regular exercise
  • glucose - lowering medication
  • insulin injections
• what is the full name of cyclic AMP

  cyclic adenosine monophosphate
• what has been the advice to companies from health advisors regarding type 2 diabetes?

  • Promote healthy lifestyles.
  • improve nutritional value of products
  • clear labeling
• what has been the response of food companies to type 2 diabetes?

  • using sugar alternatives
  • reducing sugar, salt and fat content#
• why might food companies be reluctant to make food healthier?

  • costs money
  • may cause a decrease in profits
• what is the role of kidney's?

  • remove wast products from the body
  • remove drugs from the body
  • balance the body's fluids
  • release hormone like molecules that regulate enzymes in the angiotensin-renin-aldosterone hormonal system for controlling blood pressure
  • produces active form of vitamin D for strong and healthy bones
  • control the production of red blood cells
• label the structure of the kidneys

  A) nephron

  B) fibrose capsule

  C) cortex

  D) pelvis

  E) medulla

  F) renal cortex

  G) renal vein

  H) renal artery

  I) uretter

  J) renal medulla

  K) glomerulus

  L) renal artery

  M) renal vein

  N) nephron

  O) collection duct

  
• label the feature of this

  A) tubule in centre of a group of enzyme-secreting cells

  B) pancreatic cells

  C) alpha cells

  D) beta cells

  E) blood capillary

  F) Islet of Langerhans

  
• label the nephron

  A) branch of renal artery

  B) renal capsule

  C) afferent atriole

  D) globular capillary

  E) efferent atriole

  F) branch of renal vein

  G) proximal convoluted tubule

  H) loop of Henle

  I) blood capillarys

  J) distal convoluted tubule

  K) collection duct

  
• what are the stages of osmoregulation in the nephron?

  1. the formation of glomerular filtrate
  2. reabsorption of glucose and water by the proximal convoluted tubule
  3. maintaining a gradient of sodium ions in the medulla by the loop of Henle
  4. reabsorption of water by the distal convoluted tubule and collecting ducts.
• Glomerular filtrate is made

  1. Blood enters the kidney through the renal artery which branches into atrioles

  2. Each atriole enters a renal capsule of a nephron (afferent atriole)

  3. Afferent atriole splits into capillaries to form the glomerulus

  4. Glomerular capillaries merge to form efferent atriole leaving the capsule

  5. The diameter of the afferent atriole is greater than the efferent atriole so a high hydrostatic pressure is created in the glomerulus

  6. The hydrostatic pressure causes small molecules such as water, glucose and mineral ions to be squeezed out of the capillary into the nephron (glomerular filtrate)

  7. Large molecules such as blood cells and proteins remain in the capillaries